1. Field of the Invention
The invention relates to a method having the characteristics provided in the preamble of claim 1.
2. Description of the Prior Art
With modern control devices, glow plugs in diesel engines serve not only as a cold starting aid, but are also used while driving to support and optimize the combustion behavior. When operating a glow plug, special attention must be paid to ensure adherence to a target temperature required for the optimal combustion behavior of the diesel engine. Too low a plug temperature results in less than optimal combustion and increased emission of harmful substances, while exceeding the target temperature puts unnecessary stress on the glow plug and shortens the service life thereof.
The temperature dependence of the electric resistance can be used to control glow plugs to a target temperature. In such control methods, the electric resistance of the glow plug is measured and compared to a resistance value expected for the target value of the temperature. An effective voltage that is generated by pulse width modulation of a vehicle electrical system voltage and applied to the glow plug is varied as a function of the deviation of the measured value of the electric resistance from the expected value of the electric resistance.